Piston return mechanism



Dec. 20, 1966 M. M. HANN PISTON RETURN MECHANISM 2 Sheets-Sheet 1 Filed Dec. 50, 1963 Dec. 20, 1966 M. M. HANN 3,292,553

PI STON RETURN MEGHANI SM Filed Dec. 30, 1963 2 Sheets-Sheet 2 United States PatentO 3.292.553 PISTON RETURN MECHANISM Melvin M. Harm, Rockford, Ill., assignor to Sunstrand Corporation, a corporation of Illinois Filed Dec. 30, 1963, Ser. No. 334,160. 5. Claims. (Cl. 103-162) This invention relates to axial piston hydraulic pumps and motors, and particularly to means in such devices for biasing the cylinder barrel against the port plate and for biasing the pistons toward the cam plate- It is a general object of .this invention to provide a new and useful system employing separate means for biasing the cylinder block and the pistons in opposite directions, which separate means are both grounded to a drive shaft in a hydraulic fluid translating device.

Another object of this invention is to provide a system in accordance with the foregoing objects in which an adjustable member is provided for maintaining. a predetermined clearance between the cam and piston elements under conditions in the device sufficient to otherwise force such elements away. from proper association with the cam.

It is anotherobject to provide a new and useful hydraulic piston return mechanism in a pump or motor of the type described.

Still other objects will become readily apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a longitudinal section, taken along line 11 with respect to FIG. 2 of a hydraulic fluid translating device incorporating an embodiment of the present invention;

FIG. 2 is a partial section taken along line 2-2 of FIG. 1;

FIG. 3 is a partial section taken along line 3-3 of FIG. 1; and V FIG. 4 is a longitudinal section through another embodiment or form of the invention, taken along the same general section line as the section of FIG. 1. r FIG. 2 also shows, in phantom, fluid distributioncanals and ports which are present in the device of FIG. 4, the locations of such canals and ports being specifically; described hereinbelow. A v

.While this invention is susceptibleof embodiment in many differentaforms, there are shown in the drawings and will herein be described in detail embodiments. of the invention, with the understanding that the present disclosure is to be considered as an .exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated.

Turing first to both illustrated embodiments of the invention as shown in FIGS. l-4, certain elements are similar in the two forms and are described at once as incorporated in a pump or motor of the axial piston type, including a housing indicated generally at 10, having an end plate 11 removably secured thereto by bolt means 13. Drive shaft 12 is rotatably supported at one end of housing 10 by bearings 16 and extends through cylinder block 14 to end plate 11 Where the drive shaft is rotatably mounted in bushing 15 within a recess in end plate 11.

Drive shaft 12 is drivingly connected as by splines 17 to a torque tube 18 in turn drivingly connected by splines 19 to cylinder block 14 for rotation of cylinder block 14, torque tube 18, and drive shaft 12 together. Splines 17 and 19 permit relative axial movement between shaft 12,

3,292,553 Patented Dec. 20, 1966 torque tube 18 and cylinder block 14, and a midportion of the torque tube provides a pilot for the end of the cylinder block. V

. Cylinder block 14 includes pistons 21, two of which are shown in FIG. 1, having inner ends reciprocating within bores or cylinders 23 in cylinder block 14. Cylinders 23 are provided with hearing inserts or bushings 25 within which the pistons reciprocate. Although only two pistons are shown in any one view of the figures, it is to be understood that cylinder block .14 includes an annular plurality of axially disposed cylinders within the cylinder block, each cylinder having an innerend of a piston reciprocating therein. It will be apparent from the discussions below that there are nine pistons in the annular series inthe illustrated embodiment; however, any number of pistons and cylinders may be .used, as will be recognized by those in the art. p

One end of cylinder block 14 has a bearing plate 26 pinned thereto for rotation therewith. Facing the other face of bearing plate 26 is .a port plate 27 which is pinned by pin 28 to end plate 11. Bearing plate 26 is rotatably slidable in facial contact with port plate 27. Urging of cylinder block 14 axially to the left relative to shaft 12, as viewed in FIGS. l0! 4, will tend to hold bearing plate 26 against separation from port plate 27 Cam plate 31 is mounted within housing 10 facing the other end of cylinder block 14. for pivotal movement about an axis transverse to and intersecting the axis of drive shaft. 12. The pivotal mounting of. cam plate 31 is provided bytrunnions (not shown) secured to housing 10 with the pivotal axis of the cam plate generally horizontal with respect to FIG. 2. The cam plate is adapted to be pivoted about itsaxis at an incline in either direction with respect to a neutral central position for adjustment of displacement of the pistons 21 within the cylinder block cylinders 23. For this purpose an opening 10a in the wall of housing 10 is providedfor access to cam plate 31 as for linking cam plate. 31 to suitable actuating means to control the inclination of cam plate 31 as is well known. Cylinders. 23 are provided with arcuate end ports 29 (FIG. 2) and hearing plate. 26 includes complementary extensions of ports 29 .therethrough. Thepassage configuration, asviewed fromeither side of plate 26 is the same asthe passage configuration on the end .of. cylinder 14 as illustrated in FIG. 2 Plate 26 may include wear.- resistant materials on its opposing surfaces and particularly on the surface facing port plate 27 or may be entirely of suitable bearing material such as bronze.

Port plate 27 includes arcuate inlet andoutlet passages 30 passing therethrough for conducting fluid to and from passages 29 as cylinder block 14, including plate' 26, rotates. The general configuration of passages on both sides of port plate 27 is generally the same and is also generally the same as the configuration of passages to the inner face of housing end plate 11 as illustrated in FIG. 3. The high pressure passage is designated 30a and the low pressure passage is designated 3011, assuming cylinder block 14 to ,be rotated clockwise, as viewed in FIG. 2, during pumping operation. During pumping operation of the device, displacement is increased bypivoting cam plate 31 to the incline shown in FIGS. I and 4,

and high pressure passage 30a serves as the outlet for Inlet and outlet passages 30 extend through housing end plate 11 to an inlet and an outlet (not shown) in the usual manner. The inlet and outlet are connectable to conduits (not shown) for operation of the device as a pump as will be readily apparent to those skilled in the art.

The outer ends of pistons 21 are of spherical configuration and are universally connected to bearing members, such as bearing shoes, 33 which are adapted to slide upon an annular surface of a thrust 'or hearing member 32 which is backed by and annularly slidable on cam plate 31. Of course, other pistons within the motor are equipped with similar bearing shoes and Wherever pistons 21 are described in association with other members, it is to be understood that each of the pistons is associated with similar or the same members, as will be obvious to those in'theart from the description herein.

A hold-down member, such as ring 35, engages flanges 34 of bearing shoes, 33 and carries the bearing shoes in slidable contact. with bearing surface 32. Hold-down ring 35 is provided with a central bore having a concave inner surface which is slidably engaged by and receives a spherical outer surface 18a of an end portion of torque tube 18.. Torque tube 18, axially slidable on shaft 12 and with respect to cylinder block 14, when urged to the right in FIGS. 1 or 4, will carry hold-down ring 35 toward the bearing surface of cam plate 31, thereby urging bearing shoes 33 against bearing surface of plate 32.

The center of spherical surface 18a in the embodiments illustrated falls on the plane containing the centers of the universal joints of pistons 21 and shoes 33, i.e., the. centers of the ball ends of pistons 21, at approximately the axis of shaft 12, the axial center of spline 17, and the pivot axis of the swash plate.

In each form of the invention as illustrated in FIGS. 1 and 4, separate means are provided, each grounded on the drive shaft, for biasing the piston ends against the cam plate and for biasing the cylinder block against the port plate- Turning first to the embodiment of FIG. 1, biasing means in the form of springs 38 and 39 provide the biasing forces. In order to maintain the bearing shoes 33 against bearing member 32, one of the biasing means, i.e., coiled compression spring 38, is disposed in an annular chamber 42 between drive shaft 12 and torque tube 18. Spring 38 bears at one end against a shoulder on torque tube 18 for urging torque tube 18 to the right and is grounded at the other end against an outward annular projection 43 of a sleeve 44. Sleeve 44 is grounded against. axial movement on shaft 12 between a circumferential shoulder 45 on shaft 12 and a snap ring 46 contained in groove 47 in shaft 12. Abutment of sleeve 44 against snap ring 46 grounds spring 38 against shaft 12.

The other biasing means, i.e., compression spring 39, is provided for biasing cylinder block 14,- including hearing plate 26, against port plate 27. Spring 39 is contained in chamber 50 between sleeve 44 and cylinder block 14 and is grounded at one end against projection 43 of sleeve 44. The other end of spring 39 bears against a ring member 51 which abuts a snap ring 52 secured in a groove in cylinder block 14. A11v extension of member 51 provides a pilot for hearing plate 26.

As the device is operated as a pump, rotation of block 14 clockwise, as viewed in FIG. 2,. causes fluid to be drawn in through-inlet or intake 30b and to be forced from the device .via 'outlet 30a. Rotation. of shaft 12 causes rotation of torque tube 18 and cylinder block 14 relative to cam plate 31. Springs 38 and 39, respectively, maintain proper running or sliding association of shoes 33 with bearing member 32 and bearing plate 26 with port plate 27.

Turning now to FIG. 4, otherseparate biasing means are provided for maintaining contact ofv the pistons with the cam plate and the cylinder block with the port member. First, for urging the piston ends and slippers toward the cam plate, thereis provided a hydraulic system *4 which includes an annular hydraulic chamber 54 having its inner and outer diameters respectively defined by shaft 12 and cylinder block 14, respectively, and having its axial limits respectively defined by torque tube 18 and ring 55, or more specifically by O-rings 56 in grooves 57 on shaft 12 and in grooves 58 on torque tube 18 or ring 55. Ring 55 is grounded against axial sliding to the left, as viewed in FIG. 4, by snap ring 59 in groove 60 around shaft 12. It will be apparent that torque tube 18 is urgeable to the right by pressure within chamber 54. In order to supply fluid pressure to chamber 54, a fluid supply passage 61 is provided extending from chamber 54 through block 14 and bearing plate 26 to an an nular groove 62 in the surface of bearing plate 26 facing port plate 27. It will be seen in FIG. 2 that annular groove 62 has been illustrated in phantom on the butt end of cylinder block 14, which butt end has the same general configuration as the face of bearing plate 26 disposed against port plate'227 except that annular groove 62 is absent on cylinder block 14. A similar annular groove 63 is provided in the face of port plate 27 facing annular groove 62 and the two annular grooves cooperate to define an annular passageway in communication with passage 61 andwith a passage 64. Passage 64 extends through port plate 27 and end.

plate 11 to the high pressure outlet passage 30a. Passage 64 is an elongate passage which is narrowerv than and generally parallel to the portion of passage 30a extending through port plate 27. Passage 64 maintains constant communication between high pressure passage 30a and the conduit formed by grooves 62 and 63, thereby main taining pressure in hydraulic chamber 54 during operation of the device for urging torque tube 18 to the right forcing slippers 34 toward bearing member 32.

For urging cylinder block 14 to the left and for maintaining facial contact between bearing plate .26 and port plate 27,a second biasing means in the form of a spring washer such as a Belleville spring 67, is provided between an anchor ring 68, abutting snap ring 59, and an outward annular projection 69 of a bearing plate guide sleeve 70 which in turn abuts a snap ring 71 secured in a groove in cylinder block 14. An extension of sleeve 70 pilots bearing plate 26. TheBelleville spring 67 illustrated in FIG. 4 is an annular member having an open C crosssection configuration in its noncompressed form with the C configuration opening more as the spring is compressed, e.g., to the very wide open C configuration illustrated in FIG. 4. The C configuration of the compressed spring tends to close under tension of the spring metal to expand the spring to a thicker, more closed C configuration. Spring 67, therefore, defines a compression spring between ring 68 and sleeve 70, urging block 14 to the left in FIG. 4. p

. In each form of the invention illustrated, an auxiliary piston return is provided in the form of an annular shim 74 (FIG. 1) or 75 (FIG. 4) which functions as a spacer blocking return of shoes 33 away from bearing member 32 and thereby retaining shoes 33 in close association or contact with the bearing surface of cam plate 31. The spacer 74 in FIG. 1 is a washer member between an end of torque tube 18 and the outwardly projecting flange 43 of sleeve 44 and prevents return of torque tube 18 to the left greater than a predetermined distance, thereby establishing a running clearance between shoes 33 and bearing member 32 and also determining the maximum opening betweenshoe flanges 34 and hold down ring 35 carrying the shoes 33. The running clearance is maintained by spacer 74, especially during periods of abnormal operation when the force necessary to return pistons 21 grounded ring 55. 3 Ring 55 grounds the crushed washer 75 to drive shaft 12. Washer 75 is illustrated as having been compressed to a thickness determining the maximum opening that can be obtained between slippers 33 and retaining ring 35 and establishing the running clearance for slippers 33 against the bearing surface of the cam plate. The crushed washer functions as an adjusted shim so that during periods of operation when the piston return pressure in chamber 54 may be too low to return the pistons against'the' cam plate, the fixed clearance established by crushed washer 75 assures that slippers 33 are maintained in.close association or contact with cam plate bearing member 32. i

Washer 75 is capable of compensating for tolerance build-up within the device. During manufacture or assembly of such a device as shown in FIG. 4, the elements are loaded from the open end of housing with end plate 11 removed. A gasket 76 and end plate 11 are then positioned for closure of housing 10 and bolts 13 are used to pull end plate 11 against the end of housing 10 with gasket 76 therebetween. Where a plurality of similar units are to be made, it will be seen that tolerances of any of the individual pieces slightly olf of specified precise dimensions could build up and create too little or too much running room between the shoes 33 and the bearing member 32, creating undue wear in either instances. The crushed washer 75 establishes the desired precise clearances.

The crushed washer 75 may readily be adjusted to proper thickness, for example, by employing a gasket 76 of a thickness conforming with the desired clearance between elements within the device, e.g., a few thousandths of an inch. In such instance, the device is first assembled without gasket 76 and with end plate 11 pulled tight against the end of housing 10, thereby compressing or crushing the compressible washer 75 to a thickness eliminating all clearances between sliding members. End plate 11 is then removed and gasket 76 is inserted. End plate 11 is replaced and tightened against gasket 76 by bolts 13. Thus, a predetermined running clearance equal to the thickness of gasket 76 is established within the device. The washer does not resiliently return to its original thickness.

The adjusted spacer shown in the form of crushed washer 75 is preferably an adjustable member which is adjustable by compression through a range of thicknesses. The force necessary for compressing the adjustable member is readily obtainable by tightening end plate 11 in its closing position on housing 10 but is substantially greater than any axial force which will be placed upon the member after its adjustment during operation of the device. The adjustable member, after being adjusted to the desired thickness, will not further be compressed during operation. It may be used in either embodiment.

Although the invention has been exemplified with particular reference to a hydraulic pump, the principles can also be applied to a motor. The principles are further applicable to a variety of fluid energy translating devices of fixed or variable displacement, e.g., variable on both sides of a neutral position. In such use, suitable arrangement should be made to maintain chamber 54 in communication with the high pressure line.

I claim:

1. An axial piston hydraulic pump or motor device comprising a housing, a rotatable cylinder block mounted in said housing, an annular series of axially disposed cylinders within said block, a series of pistons having inner ends reciprocating within said cylinders, a drive shaft rotatably mounted in said housing extending through said cylinder block, a torque tube in said housing between said shaft and cylinder block, a first spline connection between the cylinder block and torque tube, a second spline connection between said shaft and torque tube, bearing means in said housing restricting said drive shaft against axial movement, a cam plate mounted in said housing at one end of said cylinder block and having a bearing face inclined to one end of the cylinder block, said pistons having spherical outer ends, a series of shoes universally mounted on the spherical outer ends of the pistons and having a bearing face engaging the bearing face on said cam plate, ports communicating the cylinders with the opposite end of said cylinder block, a port plate in the housing having inlet and outlet passages adjacent the opposite end of the cylinder block communicating successively with said cylinder ports upon rotation of the cylinder block, a hold-down ring carrying said bearing shoes, a spherical surface on said torque tube engaging the hold-down ring, an axially expandable chamber grounded on said shaft at one end and biasing said torque tube at the other end, means for supplying fluid for expanding said chamber, and resilient means grounded on said shaft at one end and bearing against said cylinder block at the other end to urge the block toward the port plate.

2. The combination of claim 1, wherein the spherical center of the spherical surface being located at the approximate midpoint of said second spline and falling upon the axis of said shaft at the point where the shaft axis pierces the plane containing the centers of the spherical piston ends.

3. An axial piston hydraulic pump or motor device comprising: a housing, a port plate in said housing having inlet and outlet passages therein, a rotatable cylinder block mounted in said housing slidably engaging said port plate, an annular series of axially disposed cylinders Within said block, a series of pistons having inner ends reciprocable within said cylinders, a drive shaft rotatably mounted in said housing and extending through said cylinder block, a torque tube in said housing between said shaft and said cylinder block, first spline means interconnecting the shaft and said torque tube, second spline means interconnecting said torque tube and said cylinder block, said torque tube having a generally spherical portion extending from one end of said cylinder block, a pilot member on said torque tube separate from said splines for radially supporting said cylinder block, a cam plate mounted in said housing at one end of said cylinder block and having an inclined bearing face, said pistons having generally spherical outer ends, bearing shoes universally mounted on the spherical piston ends, each having a bearing face slidably engaging said cam face, a hold-down ring engaging said bearing shoes, and means biasing the spherical surface on said torque tube in engagement with said hold-down ring.

4. A hydraulic fluid translation device including a housing, a drive shaft mounted for rotation in said housing, a cylinder block mounted for rotation with said drive shaft, a plurality of pistons with inner ends disposed for reciprocation within cylinders in the block and protruding therefrom at one end of the block, an inclined cam plate facing said one end of said block, a bearing surface on said cam plate, bearing means on the outer ends of said pistons adapted to slidably follow said bearing surface, inlet and outlet port means communicating successively with ports from said cylinders upon rotation of the cylinder block, hold-down means axially movable relative to said cylinder block and engaging said bearing means, said hold-down means being movable toward and away from a position retaining said bearing means in engagement with said bearing surface, means on the shaft defining between the shaft and said cylinder block an expandable chamber means grounded on said shaft and adapted to receive fluid acting against said hold-down means to move said holddown means to said position upon expansion of said chamber, a portion of said hold-down means being slidable in said chamber, and means interconnecting aid chamber means with the high pressure one of said inlet and outlet.

5. The device of claim 4, including adjusted means limiting the extent of collapse of said chamber in the chamber.

References Cited by the Examiner UNITED STATES PATENTS Vicke-rs 103-162 Gabriel 103-162 Mott 103-162 Gabriel 103-162 Budzich 103-162 Vetter 103162 Stewart 103162 8 3,173,376 3/1965 Hulman et a1. 103162 3,191,543 6/1965 Hannetal. 103--162 FOREIGN PATENTS 855,582 12/1960 Great Britain.

906,357 9/1962 Great Britain.

MARK NEWMAN, Primary Examiner.

DONLEY J. STOCKING, SAMUEL LEVINE,

' V E2caminers. J. C. MUNRO, W. L. FREEH, Assistant Examiners. 

1. AN AXIAL PISTON HYDRAULIC PUMP OR MOTOR DEVICE COMPRISING A HOUSING, A ROTATABLE CYLINDER BLOCK MOUNTED IN SAID HOUSING, AN ANNULAR SERIES OF AXIALLY DISPOSED CYLINDERS WITHIN SAID BLOCK, A SERIES OF PISTONS HAVING INNER ENDS RECIPROCATING WITHIN SAID CYLINDERS, A DRIVE SHAFT ROTATABLY MOUNTED IN SAID HOUSING EXTENDING THROUGH SAID CYLINDER BOLCK, A TORQUE TUBE IN SAID HOUSING BETWEEN SAID SHAFT AND CYLINDER BLOCK, A FIRST SPLINE CONNECTION BETWEEN THE CYLINDER BLOCK AND TORQUE TUBE, A SECOND SPLINE CONNECTION BETWEEN SAID SHAFT AND TORQUE TUBE, BEARING MEANS IN SAID HOUSING RESTRICTING SAID DRIVE SHAFT AGAINST AXIAL MOVEMENT, A CAM PLATE MOUNTED IN SAID HOUSING AT ONE END OF SAID CYLINDER BLOCK AND HAVING A BEARING FACE INCLINED TO ONE END OF THE CYLINDER BLOCK, SAID PISTONS HAVING SPHERICAL OUTER ENDS, A SERIES OF SHOES UNIVERSALLY MOUNTED ON THE SPHERICAL OUTER ENDS OF THE PISTONS AND HAVING A BEARING FACE ENGAGING THE BEARINGS FACE ON SAID CAM PLATE, PORTS COMMUNICATING THE CYLINDERS WITH THE OPPOSITE END OF SAID CYLINDER BLOCK, A PORT PLATE IN THE HOUSING HAVING INLET AND OUTLET PASSAGES ADJACENT THE OPPOSITE ENDS OF THE CYLINDER BLOCK COMMUNICATING SUCCESSIVELY WITH SAID CYLINDER BLOCK COMMUNICATING THE CYLINDER BLOCK, A HOLD-DOWN RING CARRYING SAID BARING SHOES, A SPHERICAL SURFACE ON SAID TORQUE TUBE ENGAGING THE HOLD-DOWN RING, AN AXIALLY EXPANDABLE CHAMBER GROUNDED ON SAID SHAFT AT ONE END AND BIASING SAID TORQUE TUBE AT THE OTHER END, MEANS FOR SUPPLYING FLUID FOR EXPANDING SAID CHAMBER, AND RESILIENT MEANS GROUNDED ON SAID SHAFT AT ONE END AND BEARING AGAINST SAID CYLINDER BLOCK AT THE OTHER END TO URGE THE BLOCK TOWARD THE PORT PLATE. 